Why does Max have a new girlfriend in this film? Ignoring that it's been around ten years, Roxanne probably doesn't even exist in this continuity. The movie is main Disney timeline, Roxanne is from the Goof Troop-verse.
Another plausible explanation is that Roxanne was Max's girlfriend when he was in high school, and, realistically, you almost never stay with the first person you fall in love with, so it is possible that Max at one point broke up with Roxanne.
Santa Claus may think that Scrooge finally deserves the bagpipe. He has made cookies for Huey, Dewey and Louie and presumably spent quite a bit of money on Christmas decorations and food. Not bad for a stingy guy like him.
In regards to Donner being The Ditz of the reindeer: The original spelling of his name is "Dunder," so it now makes sense that he has become a complete dunderhead.
According to the map Huey, Dewey, and Louie were looking at, Santa's office is right next to the food-court. Later when Santa smells Louie's Rump Roast , he wonders aloud if they're making roast duck in the kitchen. Not only is it a Chekhov's Gag , but it also keeps the universe consistent (despiteraisingUnfortunate Implications )
This one is even lampshaded by Huey, Dewey and Louie. Scrooge sadly tells them that he never got a bagpipe for Christmas because his greed prevented him from being on Santa's Nice List. Why didn't he just buy one? Yes, we're talking about the stingy Scrooge, but being generous enough to get on Santa's Nice List would cost him more than buying a bagpipe.
Scrooge, despite his greed, carries a lot of sentiment to his belongings, most of his money bin consists of coins with some memorable link to this past. Getting bagpipes meant more as a gift and just in the general spirit of Christmas, especially when it means getting debunked as a "Naughty Listed" selfish miser.
Building on this, Scrooge's response to Dewey's question about why doesn't he just buy what he wanted is quite telling. "You cannot buy being on Santa's list". The show DuckTales (1987) hinted that Scrooge takes great pride in his ability to earn everything fair and square. For him, it's the thrill of realizing he's been rewarded for his hard work. It's not the bagpipes that he wants. It's what it represents to him; he earned it fair and square for being a good person. That's why he doesn't just buy a set of bagpipes; what would be the point of owning it if he didn't earn it in some way?
Do Huey, Dewey and Louie think adding themselves to Santa's Nice List will trick him? If nothing else, the differences in the writing would give them away.
Santa's Nice List has nothing but first names. How can he tell the children with the same first name apart?